<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    let number = prompt('请输入一个星期数:')
    switch (number) {
      case '星期一':
        if (number === '星期一') {
          document.write('monday')
          break;
        }
      case '星期二':
        if (number === '星期二') {
          document.write('tuesday')
          break;
        }
      case '星期三':
        if (number === '星期三') {
          document.write('Wednesday')
          break;
        }
      case '星期四':
        if (number === '星期四') {
          document.write('Thursday')
          break;
        }
      case '星期五':
        if (number === '星期五') {
          document.write('Friday')
          break;
        }
      case '星期六':
        if (number === '星期六') {
          document.write('Saturday')
          break;
        }
      case '星期天':
        if (number === '星期天') {
          document.write('Sunday')
          break;
        }
      default:
        alert('您是否输入错误')
        break;
    }
  </script>
</body>

</html>